| 1. |
- Weigelt, G., et al.
(författare)
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VLTI-MATISSE chromatic aperture-synthesis imaging of eta Carinae's stellar wind across the Br alpha line Periastron passage observations in February 2020
- 2021
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 652
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Tidskriftsartikel (refereegranskat)abstract
- Context. Eta Carinae is a highly eccentric, massive binary system (semimajor axis similar to 15.5 au) with powerful stellar winds and a phase-dependent wind-wind collision (WWC) zone. The primary star, eta Car A, is a luminous blue variable (LBV); the secondary, eta Car B, is a Wolf-Rayet or O star with a faster but less dense wind. Aperture-synthesis imaging allows us to study the mass loss from the enigmatic LBV eta Car. Understanding LBVs is a crucial step toward improving our knowledge about massive stars and their evolution. Aims. Our aim is to study the intensity distribution and kinematics of eta Car's WWC zone. Methods. Using the VLTI-MATISSE mid-infrared interferometry instrument, we perform Br alpha imaging of eta Car's distorted wind. Results. We present the first VLTI-MATISSE aperture-synthesis images of eta Car A's stellar windin several spectral channels distributed across the Br alpha 4.052 mu m line (spectral resolving power R similar to 960). Our observations were performed close to periastron passage in February 2020 (orbital phase similar to 14.0022). The reconstructed iso-velocity images show the dependence of the primary stellar wind on wavelength or line-of-sight (LOS) velocity with a spatial resolution of 6 mas (similar to 14 au). The radius of the faintest outer wind regions is similar to 26 mas (similar to 60 au). At several negative LOS velocities, the primary stellar wind is less extended to the northwest than in other directions. This asymmetry is most likely caused by the WWC. Therefore, we see both the velocity field of the undisturbed primary wind and the WWC cavity. In continuum spectral channels, the primary star wind is more compact than in line channels. A fit of the observed continuum visibilities with the visibilities of a stellar wind CMFGEN model (CMFGEN is an atmosphere code developed to model the spectra of a variety of objects) provides a full width at half maximum fit diameter of the primary stellar wind of 2.84 +/- 0.06 mas (6.54 +/- 0.14 au). We comparethe derived intensity distributions with the CMFGEN stellar wind model and hydrodynamic WWC models.
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| 2. |
- Chiavassa, A., et al.
(författare)
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The extended atmosphere and circumstellar environment of the cool evolved star VX Sagittarii as seen by MATISSE star
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 658
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Tidskriftsartikel (refereegranskat)abstract
- Context. VX Sgr is a cool, evolved, and luminous red star whose stellar parameters are difficult to determine, which affects its classification.Aims. We aim to spatially resolve the photospheric extent as well as the circumstellar environment.Methods. We used interferometric observations obtained with the MATISSE instrument in the L (3-4 mu m), M (4.5-5 mu m), and N (8-13 mu m) bands. We reconstructed monochromatic images using the MIRA software. We used 3D radiation-hydrodynamics simulations carried out with (COBOLD)-B-5 and a uniform disc model to estimate the apparent diameter and interpret the stellar surface structures. Moreover, we employed the radiative transfer codes OPTIM3D and RADMC3D to compute the spectral energy distribution for the L, M, and N bands, respectively.Results. MATISSE observations unveil, for the first time, the morphology of VX Sgr across the L, M, and N bands. The reconstructed images show a complex morphology with brighter areas whose characteristics depend on the wavelength probed. We measured the angular diameter as a function of the wavelength and showed that the photospheric extent in the L and M bands depends on the opacity through the atmosphere. In addition to this, we also concluded that the observed photospheric inhomogeneities can be interpreted as convection-related surface structures. The comparison in the N band yielded a qualitative agreement between the N-band spectrum and simple dust radiative transfer simulations. However, it is not possible to firmly conclude on the interpretation of the current data because of the difficulty in constraing the model parameters using the limited accuracy of our absolute flux calibration.Conclusions. MATISSE observations and the derived reconstructed images unveil the appearance of VX Sgr's stellar surface and circumstellar environment across a very large spectral domain for the first time.
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| 4. |
- Murphy, M. P., et al.
(författare)
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Guidelines for measuring reactive oxygen species and oxidative damage in cells and in vivo
- 2022
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Ingår i: Nature Metabolism. - : Springer Science and Business Media LLC. - 2522-5812. ; 4:6, s. 651-662
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Tidskriftsartikel (refereegranskat)abstract
- Multiple roles of reactive oxygen species (ROS) and their consequences for health and disease are emerging throughout biological sciences. This development has led researchers unfamiliar with the complexities of ROS and their reactions to employ commercial kits and probes to measure ROS and oxidative damage inappropriately, treating ROS (a generic abbreviation) as if it were a discrete molecular entity. Unfortunately, the application and interpretation of these measurements are fraught with challenges and limitations. This can lead to misleading claims entering the literature and impeding progress, despite a well-established body of knowledge on how best to assess individual ROS, their reactions, role as signalling molecules and the oxidative damage that they can cause. In this consensus statement we illuminate problems that can arise with many commonly used approaches for measurement of ROS and oxidative damage, and propose guidelines for best practice. We hope that these strategies will be useful to those who find their research requiring assessment of ROS, oxidative damage and redox signalling in cells and in vivo. Reactive oxygen species (ROS) have important roles in health and disease, but are chemically complex and difficult to measure accurately. This consensus statement proposes guidelines and best practices on the nomenclature and assessment of ROS, oxidative reactions and oxidative damage in cells, tissues and in vivo.
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| 5. |
- van der Velden, Jos L., et al.
(författare)
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TGF-β1-induced deposition of provisional extracellular matrix by tracheal basal cells promotes epithelial-to-mesenchymal transition in a c-Jun NH2-terminal kinase-1-dependent manner
- 2018
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Ingår i: American Journal of Physiology: Lung Cellular and Molecular Physiology. - : American Physiological Society. - 1522-1504 .- 1040-0605. ; 314:6, s. 984-997
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Tidskriftsartikel (refereegranskat)abstract
- Epithelial cells have been suggested as potential drivers of lung fibrosis, although the epithelial-dependent pathways that promote fibrogenesis remain unknown. Extracellular matrix is increasingly recognized as an environment that can drive cellular responses in various pulmonary diseases. In this study, we demonstrate that transforming growth factor-β1 (TGF-β1)-stimulated mouse tracheal basal (MTB) cells produce provisional matrix proteins in vitro, which initiate mesenchymal changes in subsequently freshly plated MTB cells via Rho kinase-and c-Jun NH2-terminal kinase (JNK1)-dependent processes. Repopulation of decellularized lung scaffolds, derived from mice with bleomycin-induced fibrosis or from patients with idiopathic pulmonary fibrosis, with wild-type MTB cells resulted in a loss of epithelial gene expression and augmentation of mesenchymal gene expression compared with cells seeded into decellularized normal lungs. In contrast, Jnk1-/- basal cells seeded into fibrotic lung scaffolds retained a robust epithelial expression profile, failed to induce mesenchymal genes, and differentiated into club cell secretory protein-expressing cells. This new paradigm wherein TGF-β1-induced extracellular matrix derived from MTB cells activates a JNK1-dependent mesenchymal program, which impedes subsequent normal epithelial cell homeostasis, provides a plausible scenario of chronic aberrant epithelial repair, thought to be critical in lung fibrogenesis. This study identifies JNK1 as a possible target for inhibition in settings wherein reepithelialization is desired.
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